Technology

CEC issues final report on OMEGA System

Rendering of an OMEGA installation at a coastal urban wastewater treatment center

he California Energy Commission (CEC) has just issued their “final” report on the Offshore Membrane Enclosures for Growing Algae (OMEGA) approach to algae cultivation and wastewater remediation. Outlining the research findings for the multi-year OMEGA project, the report is available for download on the CEC’s website.

According to the report’s Primary Author, Dr. Jonathon Trent, “The report summarizes most of the work we did over the last few years, although it does not include our more detailed techno-economic analysis, nor does it include our research on wastewater recovery as potable water (Desalgae). These latter two results will be published soon…”

The goal of the OMEGA project was to demonstrate that an ocean deployed, floating PBR inoculated with freshwater algae can produce sufficient lipids for conversion to fuel to be economically feasible and appropriately scalable so the technology may be transferred to commercial or other government sectors.

OMEGA photobioreactor tubes with swirl vanes

The researchers in this study took the position that, at least for coastal cities, the most plausible answer to the question of how to make the massive amounts of biofuels needed to displace significant quantities of fossil fuels without competing with agriculture will be to 1) use microalgae as the feedstock, 2) grow the microalgae on domestic wastewater, and 3) locate the cultivation system offshore in the vicinity of existing wastewater outfalls.

The feasibility of an enormous offshore algae cultivation system will depend on overcoming major challenges inherent in algae cultivation, in finding appropriate sites and engineering offshore systems that can cope with extreme conditions at these sites, and in many countries, navigating the environmental and political bureaucracies, which may pose the greatest difficulty in testing the new technology. It is well established that the economic challenges for biofuels are daunting if not impossible to overcome.

In the OMEGA system, oil-producing freshwater algae are grown in flexible, clear plastic PBRs attached to a floating infrastructure anchored offshore in a protected bay. Wastewater and CO2 from coastal facilities provide water and nutrients. The surrounding seawater controls the temperature inside the PBRs and kills algae that escape from the system.

The salt gradient between seawater and wastewater drives forward osmosis, to concentrate nutrients and facilitate algae harvesting. The OMEGA infrastructure also supports aquaculture and provides surfaces for solar panels and access to offshore wave generators and wind turbines. Integrating algae cultivation with wastewater treatment, CO2 sequestration, aquaculture, and other forms of alternative energy creates an ecology of technologies in which the wastes from one part of the system are resources for another.

The OMEGA team consisted of scientists and engineers from a variety of public and private organizations. The team attempted to maintain an “open source” model in the dissemination of their results and welcomed contributions from colleagues and collaborators with interests in marine biology, ecology, engineering, environmental studies, economics, and public policy.

The project was divided into three phases. In the first phase, ideas about possible OMEGA materials and designs, deployment and operation, as well as environmental constraints and concerns, were considered and discussed, which led to technical memoranda assembled into a report.

In the second phase, a functional floating 110-liter prototype system was developed in a seawater tank at a research facility in Santa Cruz and then scaled up to 1,600 liters in seawater tanks at a wastewater treatment plant in San Francisco. In the third phase, the results were evaluated and reported in a series of technical papers based on experiments and analyses in phases I & II.

According to the researchers, economic and financial evaluations, based on the limited data available, show that OMEGA compares favorably with other algae production systems. The advantage of OMEGA is that it eliminates land use, provides convenient access to wastewater and advanced wastewater treatment, contributes to carbon capture and sequestration (CCS), and creates a multifunctional offshore platform.